As a thriller, David Koepp's 'Secret Window' is more interesting than thrilling.

The story it adapts -- Stephen King's "Secret Window, Secret Garden," from his Four Past Midnight collection -- dealt in psychological suspense with a whiff of the supernatural; Koepp dispenses with the supernatural. King writes what he knows, and what he knows best is writers. Mort Rainey is one of many conflicted and/or haunted scribes in the King portfolio, a successful pulpist whose marriage has gone south and who wakes up one morning in his cabin on the lake to find himself accused of plagiarism. A man in black, John Shooter, claims that Mort stole his story "Secret Window," though it was first published in 1995 and Shooter says he wrote it in 1997. One would think this fact would settle the argument. But men in black, in King's fiction, don't give up that easily.

Since few people would care overmuch about a story concerning a writer who didn't steal a story, Shooter is turned into a grinning psycho who isn't above dispatching innocent bystanders or household pets with the nearest screwdriver. As played by John Turturro, Shooter has a gentle, insinuating drawl (he's from Mississippi), and though we don't actually see him do anything terribly brutal, Turturro gives him a knife-edge aura of threat, which has served the actor well since he beat a penguin to death in Five Corners. Shooter works well as a nagging doubt in the writer's mind, either real or imaginary.

Right at the beginning, Mort walks into a hotel room and confronts his wife Amy in bed with another man. That's about as much animation as we see from Johnny Depp for most of the movie. He plays Mort as a slightly dazed eccentric grateful for writer's hours -- he gets to take naps and eat Doritos instead of working on his new story, which seems to be influenced by Amy's infidelity. But then "Secret Window," written in the early days of his relationship with Amy, is also about a cuckold -- this one driven to murder. Once again, Depp slouches into a piece of mainstream entertainment and takes every opportunity to amuse himself. Mort's shambling depression, in Depp's hands, becomes a witty portrait of dissolution.

Which is not to say Secret Window is worth much more than the price of a rental. Writer/director David Koepp, a screenwriter-for-hire who has directed two interesting but flawed thrillers (The Trigger Effect and Stir of Echoes), starts things off at a brisk clip, and the scenes between Depp and Maria Bello (as his estranged wife) and Timothy Hutton (as her clownish new beau) are well-drawn character comedy. (Mort cringes at the sound of his wife's voice the way a vampire flinches at a cross.) But there's too much stale horror crappiness, like a black character (Charles S. Dutton) who's so obviously in the movie just to be killed that he might as well be called Dick Hallorann, and various misfortunes involving corpse disposal, and scenes with Johnny Depp investigating strange noises at night while holding a flashlight or a poker, which even he can't redeem.

As for the Twist at the End, all it did for me was make me crave some corn on the cob (that'll make sense if you ever see it). Secret Window at least spares us King's long-winded post-game exposition, which reads like a serious challenger to Psycho's throne in the category of Unnecessarily Explicit Explanations of Someone's Neurosis. This writer-director does have serious things on his mind -- his Trigger Effect offered some note-perfect episodes of tension emerging entirely out of the characters' demons. But Koepp isn't accomplished enough to pull much ambiguity or allegory out of horror-fantasy, it appears.

'Secret Window' feels like the work of one of King's writer protagonists, Paul Sheldon of 'Misery,' who was famous for romantic pulp but yearned to write something more meaningful. No one's forcing Koepp to make pulp. No one's forcing King, either.